Catheters are used for a large number of surgical procedures. For example, in many relatively new surgical techniques, e.g., endoscopic surgery, a small opening is made in the patient, and one or more catheters or cannulas are inserted into the opening to provide various working passageways through which small surgical instruments can be advanced into the patient to perform the particular procedure. To keep the opening as small as possible, it is desirable to minimize the diameter of the catheters.
Not surprisingly, it is sometimes advantageous that as the catheter is being positioned in the patient, the catheter be able to bend at predetermined locations, either to aid in advancing the catheter along a tortuous path or to avoid an obstructing object inside the patient. Simply pre-bending a catheter at a predetermined location on the catheter, however, can interfere with inserting the catheter along a straight-line path, and is therefore oftentimes undesirable.
Accordingly, past attempts have been made to make an entire catheter out of a flexible material. These devices sometimes provide a means for bending the catheter. One example of such a means is a manipulable wire connected to the catheter at the location where the bend is to occur. The catheter can be bent at the point of wire connection by pulling the wire.
Unfortunately, such devices are subject to buckling and do not always bend in proportion to the pulling force of the wire, making it difficult to reliably gauge the amount of pulling force necessary to bend the catheter an appropriate amount. Also, such catheters often lack structural strength to the extent that they can undesirably bend at unintended locations.
To overcome the structural strength problems mentioned above, catheters may be made of thin-walled strong and rigid material, such as steel. These catheters, however, cannot easily conform to the contours of a body vessel or duct. It is desirable for a catheter to conform to follow a body vessel or duct.
Accordingly, it is an object of the present invention to provide a catheter which can be bent at one or more predetermined location on the catheter. Another object of the present invention is to provide a small diameter, thin-walled bendable catheter that has a relatively high degree of structural strength. Further, it is an object of the present invention to provide a catheter which is easy to use and cost-effective to manufacture.